Separation of volatile constituents from crude soaps



Patented July 3, 1934 SEPARATION or VOLATILE CONSTITUENTS raoM CRUDE soars Christoph Beck, Ludwigshafen-on-the-Rhine, and Helmut Weissbach and Heinrich Dickmann, Mannheim, Germany, assignors to I. G. Farbenlndustrie Aktiengesellschaft, Frankfort-onthe-Main, Germany No Drawing. Application February 12, 1932,

Serial Np. 592,648. In Germany February 14,

7 Claims. (01. 202-53) The present invention relates to the separation of volatile constituents from crude soaps.

We have found that aqueous crude alkali metal soaps prepared from materials containing fatty acids of high molecular weight,,e. g. thosexhaving at least 10 carbon atoms, or mixtures thereof, such as products or the oxidation of aliphatic hydrocarbons of high molecular weight and of mixtures thereof, or fats, oils or waxes 01 natural origin can be freed from volatile substances of.

high boiling point contained therein in a manner which is simple industrially by heating the aqueous crude soaps to the meltingtemperature' oi the anhydrous soaps in a closed vessel so that an initial increased pressureis generated and the mass remains continually liquid, releasing the pressure and then removing the volatile constituents from the anhydrous melt at the same or a more elevated temperature bydistillation, if desired while employing a vacuum or while passing 0 through steamor other inert gaseous agent such as nitrogen, carbon dioxide or inert industrial waste gases. In this manner, by reason of the fact that the mass is continually.kept in the liquid state notwithstanding the removal of water, it may be readily brought without inconvenience to the temperatures necessary for the removal of the volatile substances of high boiling point. such as alcohols, aldehydes, ketones or hy .drocarbons, or mixtures thereof having a boiling point above 100 C., and the distillation of the said substances proceeds rapidly and without injurious decompositions. The minimum pressure necessary to produce this effect during the heating up to the melting temperature depends on the nature of the saponiflcation products to be worked up; in most cases pressures of from about 10 to about 30 atmospheres are suflicient, but higher pressures may be'employed. The melting temperatures, which lie generally between about 200 and about 300 C. and usually between 250 and 300 0., are also dependent on the nature of the initial materials; they'may be readf materials containing non-saponifiable constituents of high boiling point, as for example natural waxes, such as mineral waxes containing esters such as crude Montan wax, physically or chemically bleached Montan wax, or vegetal, i. e. animal or vegetable waxes, such as wool grease, sperm oil, spermaceti and the like. oxidation products of liquid or solid non-aromatic hydrocarbons, such as parafiln wax, paraflln oil or high-boiling mineral oil fractions, which oxidation products contain high molecular fatty acids,

alcohols, aldehydes and ketones, products of the.

catalytic hydrogenation of vegetal fatty acids or esters which products often contain some fatty acids and some hydrocarbons besides alcohols and may consist of esters of the said fatty acids with the corresponding saturated alcohols. The quantity of water in the said crude soaps is generally so high that a mass is obtained in the saponification which can be easily stirred by mechanical means as are usual in the soap industries. The quantity of alkali present in the crude soaps may .be equivalent to those of fatty acid present but it may. be higher or lower, the saponiilcation requiring often an excess 01' alkali and, on the other hand, may be often carried out with a lower quantity of alkali depending ,on the resistance to saponification of the initial materials and on the nature of the alkali employed.

The process may be carried out for example by first heating the aqueous saponiflcation product in a closed vessel, preferably while stirring or otherwise causing movement, until the necessary minimum pressure ascertained by a preliminary test with a small quantity in a small vessel has been produced then 'while maintaining the said pressure, which may be eflected by periodically releasing the pressure, heating the mass to the melting temperature of the anhydrous saponiflcation products and removing the water contained in the saponiilcation products in the to of water vapor by releasing the pressure.

volatile constituents then distil ed at the same or amore elevated temperature because the fused saponified mass in contrast to'an intermediately dried product is capable both of absorption of heat and degasification. The distillation may be accelerated by leading in steam or inert gases,

by the employment of a vacuum and/or by stir- 9 ring or otherwise moving the saponified mass, as for example with the aid of rotating vessels or by allowing it to flow along the walls 01' a, vessel. The'heating of the saponiflcation products to the melting temperature, the releasing of the pressure and the distillation of the volatile constituents may be carried out in batches in a pressure-tight stirring vessel capable of being heated and provided with the necessary supply and withdrawal pipes for supplying and withdrawing the saponification products and for distilling off the vapors and if desired also for blowing in steam or gases. It is of especial advantage, however, to carry out the process in a continuous manner and only to expose the product for a very short time to the high and, during a too protracted action,. injurious temperatures. For example the saponification product may be heated in a closed stirring vessel as hereinbefore described only to such an extent that the necessary minimum pressure is attained. While making use of the pressure, the mass is then led from the stirring vessel through a tube system heated to the said or higher temperatures at the end of which the fused mass is released from pressure and at the same time freed from water vapor in a chamber which is likewise heated to the said temperatures and in which the mass is subjected to distillation for the removal of impurities.- The heating of the apparatus is preferably carried out while avoiding injurious overheating, as for example by means of metal baths the temperature of which is not allowed'to exceed the predetermined lim-- its. The melt of soaps freed from volatile con stituents may be rapidly removed from the hot distillation zone by its own weight or by employ},

or water vapor that the minimum pressure pre-.

vailing during the heating is produced again and is maintained by the supply of water or water vapor until the whole has cooled to about the temperature at which. previously the said pressure had been produced by heating. In this manner a ready cooling and dissolution of the ,saponification products is rendered possible without inconvenience.

The process according to the present invention is especially suitable for separating unsaponifiable constituents of high boiling point from saponiflcation products of substances containing fatty acids, especially of oxdiation. products of aliphatic hydrocarbons of high molecular weight.

' It may also be employed, however, for the removal the direct preparation of completely anhydrous saponitlcation products from solutions thereof. Furthermore, treatments of the saponification products other than distillation which necessitate a heating of the saponiflcation products to from about 200 to 300 C. may be carried out according to the. present invention or may be combined therewith. For example the process may be used with special advantage'in the working up of oxidation products of hydrocarbons obtainable for example by the treatment of paraflin wax. paraflin oil, high-boiling mineral oil fractions or the like with nitric acid or oxides of nitrogen. If products of the said kind are heated in alkaline solution to from 200 to 250 C. under pressure for the purpose of splitting of! nitrogen.

they may be immediately afterwards freed from Efrainplei 1500 parts of an oxidation product (obtained by the treatment of 1350 parts of hard paraffin wax'with a per cent nitric acid at C. for about 8 hours) having an acid value of 128, a

saponification value of 243, a content of 17.5 per cent of unsaponiflable material and 3.1! per cent of nitrogen are mixed with 1800 parts of a 20 per cent aqueous caustic soda solution and heated to 230 C. in an autoclave while stirring. A pressure of 25 atmospheres lSzthllS produced. The soap solution is led under pressure through a spiral tube which is situated in a lead bath heated to 340 C, and is introduced, with the simultaneous release of pressure, into a vessel provided with a stirring device, a temperature of 320 C. being maintained in the said vessel. The fused saponification product leaves the vessel through a siphon arranged in the lower part thereof, while the vapors of the unsaponiflable substances to-' gether with the steam escape through an outlet pipe and are condensed. In this way 300 parts of unsaponiflable substances are obtained. The pure saponiflcation product is dissolved in water and decomposed by means of hydrochloric acid. The fatty acids which separate have the following characteristlcsj acid value 265, saponification value 2'11. content of 'unsaponiflable substances 3.1 per cent, nitrogen 0.49 per cent. distillation of these fatty acids, a part of the unsaponifiable substances remains behind in the distillation residue so. that, calculated on the initial amount, 77 per cent of fatty acids contain- During a ing only 1.6 per cent of unsaponiflable substances are finally obtained.

' Example 2 nitrogen thus produced is regulated to 5 atmospheres and kept constant by periodically releasing After separating off the nitric acid,

the pressure. 5600 parts of an oxidation product having a saponification value of 180, a nitrogen content of 2.4 per cent and a content of 25 per cent of unsaponifiable substances are obtained. The product is saponifled by heating it to 100 C. in an open vessel until carbon dioxide is-removed with 4000 parts of a 25 per cent aqueous sodium carbonatesolut-ion and then heated to from 200 to 220 C, in a pressure-tight iron container; a pressure of water vapor of from 20 to 24 atmospheres is thus set up. A small quantity of water vapor is allowed to escape from the reaction vessel until it no longer contains ammonia, that is until the nitrogen has been split oft-from the oxidation product. Then, while keeping the pressure con- 1,ees,see

steam being condensed together with the distilled unsaponr'flable substances outside the stirring vessel. The temperature of the saponification product is then increased to 310 C. After about 1 hour, 1300 parts of unsaponiiiable substances, mainly consisting of paraflln wax,have been ex-, pelled from the saponii'lcation product. The mass is cooled by pressing in about 3000 parts of cold water, withdrawn from the stirring vessel and acidified with aqueous nitric acid. In this way an upper layer of 3900 parts of dark-brown fatty acids is obtained which may be iurther worked up into pure pale fatty acids by distillation with steam in vacuo at from 0.1 to 0.01 atmosphere. The fatty acids obtained in the manner contain only from 1 to 2 per cent or unsaponiflable substances and Diner cent of nitrogen.

, Example 3 r 100 parts of wool tat having a saponification va1ue of 88 are heated while stirring in an autoclave with parts of a 20 per cent aqueous caustic soda solution and '75 parts of water. As soon as a pressure of 30 atmospheres is attained heating is continued while blowing oil steamin such a quantity that the pressure remains constant. As soon as the mass has attained a temperature of from 250 to 260 C. the pressure is completely released whereby the steam is wholly blown off. The soap in the autoclave is then heated to 350 C. while blowing through steam for facilitating the distillation oi the volatile constituents. The vapors are passed through a condenser heated to from about 70 to about 80 C. so that volatile matter distilled off is condensed.

In this manner 42.5 parts of the unsaponiflable matter contained in the wool lat'are obtained. Thesoap remaining as the distillation residue is then split with the aid of acid in any usual and convenient manner whereby 48 parts of the acids oi wool'lat are obtained which show an acid value oi. 128, a saponiflcation value of 139 and a content of unsaponiflable matter of 14.5 per cent.

Example 4 v 1000 parts oi sperm oil having a saponii'lcation.

value oi! 150 are heated in an autoclave while stirring to 200- C.-'together with 590 parts oi a 20 per cent aqueous caustic soda'solution and 530 parts of water, whereby a pressure oi 18 atmospheres is attained. The whole is then kept for 3 hours at the said temperature for rendering completethe saponiflcation, passed by the prevailing pressure into a pipe system in which it is heated to 300 C. while maintaining the pressure and then released through a second pipe system connected into a separator in which .the

temperature is kept at 300 C. The separator is provided at its bottom with a siphon from which the molten, soap is drawn oi! while the vapors are drawn oil through an outlet pipe connected to the top 0! the separator and then led to a-condenser in which they are precipitated by indirect cooling with the aid of water warmed to from 70 to C. I

In this manner, after the separation of the water, 350 parts oiunsaponii'lable material, that is almost the whole quantity of alcohols of high molecular weight contained in the original sperm oil, are obtained which alcohols show a saponiiication value of from 2 to 3 only and which therefore may find useful application without purification. :From the molten soap, the fatty acids as the aforesaid'temperature.

vunsaponiiiable matter from crude soaps the step which comprises heating an aqueous, crude soap containing volatile, unsaponifiable substances at a pressure between 10 and about 30 atmospheres to the melting point of the soap, when in the anhydrous state, releasing the pressure and then distilling on the said volatile, unsaponiiiable substances at a temperature at least as high as the aforesaid temperature.

2. In the separation, by distillation, of volatile, unsaponiilable matter from crude soaps the step which comprises heating an aqueous, crude soap containing volatile, unsaponifiable substances to from about 250 to about 300 C., at a pressure between 10 and, about 30 atmospheres, releasing the pressure and then distilling of! the said volatile, unsaponifiable substances at a "temperature at least as high as the aforesaid temperature.

3. In the separation, by distillation, oi! volatile,

unsaponifiable matter from crude soaps the step unsaponifla'ble matter from crude coaps, the step which comprises heating an aqueous, crude alkali metal soap; from the products of an oxidation of ditlicultly volatile, non-aromatic hydrocarbons and containing volatile, unsaponiflable substances, at a pressure betweenlo and about 30 atmospheres to the melting point of the soap when in the anhydrous state, releasing the pressure and then distilling oil the said volatile, unsaponiflable substances at a temperature at least as high as the aforesaid temperature.

5. In the separation, by distillation, of volatile, unsaponifiable matter from crude soaps, the step which comprises heating an aqueous, crude alkali metal so'ap, irom the products oi an oxidation of difllcultly volatile, non-aromatic hydrocarbons and containing volatile, unsaponiflable substances, at .a pressure between 10 and about 30 atmospheres to the melting point of the soap when in the anhydrous state, releasing the pressure and then distilling oil the said volatile, unsaponifiable substances with the aid of steam at a temperature at least as high as the ai'oresid temperature.

6. In the separation, by distillation, of volatile, unsaponifiable matter from crude soaps, the step which comprises heating an aqueous, crude sodium soap from the saponiflcation of products of an oxidation of paraffin and containing volatile. ,unsaponiflable" substances, to from about 250 to about 300 C. at a pressure I and about 30 atmospheres, releasing the pressure and then distilling of! the said volatile, unsaponiflable substances at a temperature at least as high between 10 .145

I 7. In theseparation, by distillation, o! volatile,

unsaponiflable matter from crude soaps, the step which comprises heating an aqueous, crude sodium soap from the saponiflcation of sperm oil and containing alcohols of sperm oil esters to 5 about 200 C. at a' pressure of about 18 atmospheres, heating the whole to about 300 (3., while maintaining the said pressure, releasing the pressure and separating the vapors formed {mm the liquid soap.

CHRISTOPH BECK.

' rHELMUT WEISSBACH.

HEINRICH DIEKMANN. 

